Towards a fully unstructured ocean model for ice shelf cavity environments: Model development and verification using the Firedrake finite element framework
Towards a fully unstructured ocean model for ice shelf cavity environments: Model development and verification using the Firedrake finite element framework
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面向冰架空腔环境的完全非结构化海洋模型：使用 Firedrake 有限元框架进行模型开发和验证
DOI：
10.1016/j.ocemod.2023.102178
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发表时间：
2023
期刊：
影响因子：
3.2
通讯作者：
Scott W
中科院分区：
文献类型：
--
作者：
Scott W
对冰流的数值研究一直认为，出口冰川和冰流的接地带(冰开始漂浮的区域)对于预测接地冰向海洋流失的速度至关重要。由于极端环境和很难进入冰架下的海洋洞穴，现场观测很少见。从卫星得出的熔融速度的估计也很难可靠地做出接近地面区域的估计。因此，海洋数值模式是研究这些关键和偏远地区的重要工具。然而，结构化网格模型的相对不灵活意味着它们可能难以在接地区附近的不规则空腔几何形状中解决这些过程。为了解决这个问题，我们提出了一个基于Firedrake有限元框架的冰架下流动的非静力非结构网格模型。我们展示了我们使用社区标准ISOMIP+Ocean 0测试案例模拟全冰架空域的能力，并将我们的结果与流行的MITgcm模型的结果进行了比较。这两个模型之间有很好的一致性，尽管它们使用了不同的离散化方案，并且熔化速率参数对网格分辨率很敏感。基于人工解方法(MMS)的验证试验表明，新的模型离散化是合理的，且具有二阶精度。使用Firedrake背后的一个主要驱动因素是自动生成的伴随模型的可用性。我们的第一个伴随计算，在理想的接地区域中，对不同输入的融化速率的敏感性进行了计算，是有希望的，并指出了未来解决关于海洋对冰架脆弱性的影响的一些重要问题的能力。
Numerical studies of ice flow have consistently identified the grounding zone of outlet glaciers and ice streams (the region where ice starts to float) as crucial for predicting the rate of grounded ice loss to the ocean. Owing to the extreme environments and difficulty of access to ocean cavities beneath ice shelves, field observations are rare. Estimates of melt rates derived from satellites are also difficult to make near grounding zones with confidence. Therefore, numerical ocean models are important tools to investigate these critical and remote regions. The relative inflexibility of structured grid models means, however, that they can struggle to resolve these processes in irregular cavity geometries near grounding zones. To help solve this issue, we present a new nonhydrostatic unstructured mesh model for flow under ice shelves built using the Firedrake finite element framework. We demonstrate our ability to simulate full ice shelf cavity domains using the community standard ISOMIP+Ocean0test case and compare our results against those obtained with the popular MITgcm model. Good agreement is found between the two models, despite their use of different discretisation schemes and the sensitivity of the melt rate parameterisation to grid resolution. Verification tests based on the Method of Manufactured Solutions (MMS) show that the new model discretisation is sound and second-order accurate. A main driver behind using Firedrake is the availability of an automatically generated adjoint model. Our first adjoint calculations, of sensitivities of melt rate with respect to different inputs in an idealised grounding zone domain, are promising and point to the ability to address a number of important questions on ocean influence on ice shelf vulnerability in the future.
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影响因子：
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